Final answer:
Meg mixed 1 part strawberry juice with 3 parts lemon juice, which means for every part of lemon juice, there is 1 over 3 part of strawberry juice.
Step-by-step explanation:
The student is asking about the ratio of strawberry juice to lemon juice in a mixture. When Meg mixed 1 part strawberry juice with 3 parts lemon juice, she used 1 part of strawberry juice for every 3 parts of lemon juice. Therefore, the number of parts of strawberry juice mixed with each part of lemon juice is 1 over 3, or ⅓, which corresponds to option a.